Write the definition of a function named checked$\_$sum that sums two numbers and checks to determine whether the sum is within an acceptable margin of error. The function should have the following parameters:

Two positional$-$only parameters, which are the numbers to sum

A parameter named target that is the expected sum

A keyword$-$only parameter named cutoff that has the default value None. If cutoff is set to a value, it defines an acceptable range within which the sum can fall. For example, if cutoff is set to $0\mathrm{.}01,$ it means the calculated sum can be within plus or minus $0\mathrm{.}01$ of the target value.

If the calculated sum is equal to target, or within the acceptable range of target, the function should return the value of target. Otherwise, the function should display "Error is too big" and return the calculated sum.